By "non-perforated" method you are referring to replacing the 2 large perforated pipes with straight pipes right? I have that done as well. If you want more cabin volume I recommend removing the secondary cats. That will def make the sound more aggressive inside and out but will add some rasp if you are ok with that.

Thanks for the suggestion. Does that void the warranty if it causes any problems? Also, how much louder does it make it on the outside? For example, I drove in a car that has the OEM Exhaust Mod (ACM/Bypass) and that was definitely too loud on the outside for me. What's the volume level when you remove the secondary cats?

The rasp is absolutely no problem for me. I actually didn't mind the rasp on the E46...